It's a Small World started as a way to promote global harmony, but 50 years later the Disney ride may be more famous for a theme song that's hard for visitors to forget — even when they want to.

The cheery tune about laughter, hopes, fears, mountains, oceans, the sun and a smile divides listeners into two camps.

"They want to kiss me or kill me," said Richard Sherman, who co-wrote "It's a Small World (After All)" with his late brother, Robert. "They either love it or hate it. They hate it because they can't get it out of their heads."

Disney is celebrating the 50th anniversary of the attraction, which was designed as a salute to UNICEF for the 1964 World's Fair in New York. The company will mark the occasion with an international sing-along on Thursday.

The song got its start when Walt Disney called the Shermans about the exhibit, then called "Children of the World." Disney's idea was to have visitors float past an array of moving dolls dressed in costumes representing their countries and singing national anthems. But it just didn't sound right.

"It was cacophony," recalled Sherman, who lives in Beverly Hills, Calif. Disney asked the duo to write a song that was simple, folksy and translatable and that advocated peace on Earth without being preachy, Sherman said.

The ride and the song were hits of the World's Fair, Sherman said. A version of the attraction was built at Disneyland in 1966, then at Disney World's Magic Kingdom, which opened in 1971. In Orlando, the 12-minute ride has endured with few changes.

It's a Small World also has been included in Disney parks in Paris, Tokyo and Hong Kong, and the company estimates that hundreds of millions of visitors have taken the ride at one of the Disney parks. But some people cannot sing its praises.

"It's great for kids, you know, with all the dolls from the different countries and the animation," said Laurie McGee, a former Disney employee who lives in Orlando. "But the music, the song, over and over and over and over — that's my issue with it."

She took her kids on the Magic Kingdom ride and they are fans, she said.

"They like it because they like to torture me," McGee said.

Mark Willard, who lives near Philadelphia and visits Disney World a few times a year, likes It's a Small World — particularly its bold, colorful visuals that were spearheaded by artist Mary Blair.

Her art had a "happy, optimistic outlook to it, which is obviously very fitting the statement of It's a Small World," Willard said.

Nuances in classic Disney attractions such as It's a Small World, Pirates of the Caribbean and Haunted Mansion pay off, he said.

"The reason they're so enjoyable to so many people over and over again is that there's so much detail in them where you can ride them many, many times and still notice things that you never saw before," Willard said.

He's OK with the music — to a point.

"It's not like it's something I'm going to listen to in my free time for hours on end," he said. "I would question someone who did that, but while I'm on the attraction itself, I enjoy it."

Walt Disney Co. started its Small World celebration last month with a website that allows users to upload their own rendition of the song and to design a figure in the style of the attraction's animatronics. The site (smallworld50.com) includes a video montage of people around the world performing the song.

Proceeds from the sales of special Small World merchandise will benefit UNICEF projects in Bangladesh, Haiti, China and Brazil.

The company also will have a rolling global celebration at its parks on Thursday, including an "It's a Small World" sing-along before the afternoon parade at the Magic Kingdom. The park's performing groups, such as the Dapper Dans and Main Street Philharmonic, will be including the tune in their appearances. Before the park opens, international cast members will gather at Cinderella Castle to perform for an appearance on ABC's "Good Morning America."

"We all like to jest that we have a love-hate relationship with it, but I think everyone loves it," said Duncan Wardle, a Disney World spokesman. "It touches people's hearts, and I think that's what's made it a global phenomenon."

Sherman has advice for naysayers, those who'd rather kill than kiss him for that song.

"I smile and I say, 'Think of the words. Think of the thought in the song and you might not be so angry.'"

Royal Caribbean Cruises is letting another of its older vessels go. The Splendour of the Seas, which was built in 1996, will leave the cruise line in 2016 after completing all of its scheduled itineraries. The 1,830-guest vessel, which currently sails South American cruises out of Santos,...